(Not Applicable)
(Not Applicable)
The present invention relates generally to pumps, and more particularly to a multiple layer diaphragm which is particularly suited for use in a pump and is adapted to possess a high level of flexibility and resiliency while being capable of withstanding an aggressive chemical environment.
Pumps, and more particularly gas driven pumps, for pumping fluids such as hydrophobic (e.g., oil based) liquids and/or hydrophilic liquids are well known in the prior art. Such gas driven pumps typically comprise a housing which defines an interior cylinder or pumping chamber. Disposed within the pumping chamber is a reciprocally moveable piston having a diaphragm attached thereto. In addition to being attached to the piston, the diaphragm is attached to the housing of the pump so as to extend between the piston and the housing. As such, the piston and the diaphragm collectively divide or segregate the pumping chamber into a pumped product portion and a pressurizable portion. In the operation of the pump, the liquid is alternately drawn into and forced from within the pumped product portion, with a gas such as carbon dioxide alternately being forced into and vented from the pressurizable portion for purposes of facilitating the reciprocal movement of the piston within the pumping chamber.
As will be recognized, in those instances when the hydrophobic, hydrophilic or other liquids with which the pump is being used are xe2x80x9caggressive chemicalsxe2x80x9d, the diaphragm must be fabricated from a material which is capable of withstanding the derogatory effects of such liquids. However, in addition to being able to withstand the aggressive chemical environment, the material used to form the diaphragm must also have enough flexibility and resiliency as is needed to properly move (i.e., stretch) during the reciprocal movement of the piston.
To provide the required attributes of durability and flexibility, the current practice in the prior art is to outfit pumps used in conjunction with aggressive chemicals with diaphragms comprising a layer of fabric impregnated with a synthetic rubber such as VITON(copyright) which is manufactured by Dupont Dow Elastomers, L.L.C. of Wilmington, Del. Though this particular synthetic rubber is formulated to withstand chemically aggressive liquids, it only possesses a relatively low level of flexibility and resiliency. As a result, the repeated stretching of the diaphragm as occurs during the normal operation of the pump tends to rapidly weaken the same, as could result in the cracking or rupture thereof. As will be recognized, such rupture would allow the undesired migration of the liquid within the pump from the pumped product portion of the pumping chamber to the pressurizable portion thereof. In an effort to strengthen the prior art diaphragm, the synthetic rubber used to fabricate the same is provided with the fabric core as indicated above.
The prior art diaphragms are typically fabricated via a molding process wherein the layer of fabric is impregnated with the VITON(copyright) or other synthetic rubber material. The diaphragm is formed such that the layer of fabric is captured between two layers of the VITON(copyright). Upon the completion of the molding process, the VITON(copyright) may be vulcanized to further strengthen the same. As indicated above, though the VITON(copyright) is capable of withstanding an aggressive chemical environment, it possesses inferior flexibility characteristics as are optimal for use in a reciprocating pump. Thus, the fabric reinforcement is adapted to strengthen the VITON(copyright) for purposes of increasing its repetitive flexibility or flexing. As will be recognized, the prior art process used to mold the VITON(copyright)/fabric core diaphragm is time consuming and costly. Additionally, the resulting diaphragm includes a large amount of VITON(copyright) which, due to its cost, makes the cost of the completed diaphragm high due to not only to the cost of the VITON(copyright), but the cost associated with the molding process as well.
Also known in the prior art are various materials such as thermoplastic elastomers which, though possessing a high level of flexibility and resiliency, are not particularly well suited to withstanding an aggressive chemical environment. Though such materials are well suited for diaphragms employed in pumps used in conjunction with non-aggressive chemicals or liquids they are typically considered to be unusable in aggressive chemical environments.
By the present invention, the Applicant has developed a pump diaphragm which combines the best attributes of synthetic rubbers such as VITON(copyright) and highly flexible thermoplastic elastomers. More particularly, the present invention relates to a diaphragm which comprises a first layer of a synthetic rubber such as VITON(copyright), and a second layer fabricated from a highly flexible or resilient thermoplastic elastomer which is disposed in laminar juxtaposition to the first layer. The diaphragm of the present invention may be installed in a pump such that the VITON(copyright) or similar synthetic rubber layer is exposed to the pumped product portion of the pumping chamber, with only the thermoplastic elastomer layer being exposed to the pressurizable portion thereof. Thus, the VITON(copyright) layer provides the requisite capability of withstanding exposure to the aggressive chemical environment, while the thermoplastic elastomer layer provides superior flexibility and resiliency. These two layers are not adhered to each other, thus allowing at least portions thereof to move relative to each other during the reciprocation of the piston. As will be recognized, the methodology employed to fabricate the diaphragm of the present invention is significantly less costly than the prior art due to the absence of a complicated molding process wherein a fabric core is impregnated with a synthetic rubber material. Thus, the present invention provides a less costly and more effective pump diaphragm useable in an aggressive chemical environment, as compared to those diaphragms currently known and used in the prior art. These and other advantages attendant to the present invention will be discussed in more detail below.
In accordance with the present invention, there is provided a pump diaphragm which is particularly suited for use in a pump having at least first and second housing sections, an interior pumping chamber, and a piston disposed within the pumping chamber. The diaphragm comprises a first layer which is formed from a first material adapted to be substantially impervious to liquids. More particularly, the first layer is preferably fabricated from a synthetic rubber which is adapted to be substantially impervious to both hydrophobic and hydrophilic liquids. One preferred synthetic rubber material from which the first layer may be formed is VITON(copyright) manufactured by Dupont Dow Elastomers, L.L.C. of Wilmington, Del.
In addition to the first layer, the diaphragm of the present invention comprises a second layer which is disposed in laminar juxtaposition to the first layer and formed from a second material adapted to possess a high level of flexibility and resiliency. The second material is preferably a thermoplastic elastomer. Exemplary thermoplastic elastomers which may be used to form the second layer include SANTOPRENE(copyright) manufactured by Advanced Elastomer Systems, L.P. of Akron, Ohio and GEOPLAS(copyright) manufactured by Geoplas, Inc. of Granville, Ohio.
In the preferred embodiment, the first layer has a generally annular configuration and includes inner and outer peripheral portions which define inner and outer peripheral edges, respectively. Similarly, the second layer has a generally annular configuration and includes inner and outer peripheral portions which define inner and outer peripheral edges, respectively.
Importantly, the outer peripheral portions of the first and second layers are formed to have complimentary configurations such that the outer peripheral portion of the second layer may be nested within the outer peripheral portion of the first layer. Similarly, the inner peripheral portions of the first and second layers are formed to have complimentary configurations such that the inner peripheral portion of the second layer may be nested within the inner peripheral portion of the first layer. As such, in the fabrication of the present diaphragm, the first and second layers are disposed in laminar juxtaposition to each other such that the outer peripheral portion of the second layer is nested within the outer peripheral portion of the first layer, with the inner peripheral portion of the second layer being nested within the inner peripheral portion of the first layer.
Though being disposed in laminar juxtaposition to each other, the first and second layers of the present diaphragm are preferably not affixed or adhered to each other, thus allowing for at least portions of the first and second layers to be moveable relative to each other. More particularly, such portions of the first and second layers are moveable relative to each other when the outer peripheral edges thereof are captured between the first and second housing sections of the pump, and the inner peripheral edges thereof are captured within the piston of the pump. As will be recognized, when the inner and outer peripheral edges of the diaphragm are captured within the piston and between the first and second housing sections, respectively, the piston and the diaphragm collectively divide or segregate the interior pumping chamber of the pump into pumped product and pressurizable portions, with the diaphragm being oriented such that the first layer is exposed to the pumped product portion and the second layer is exposed to the pressurizable portion.
In addition to the foregoing, the outer peripheral portions of the first and second layers are preferably sized relative to the first and second housing sections so as to be compressed thereby when captured therebetween. Similarly, the inner peripheral portions of the first and second layers are preferably sized relative to the piston so as to be compressed thereby when captured therein. Such compression of the inner and outer peripheral portions of the first and second layers prevent any migration of liquids from the pumped product portion of the pumping chamber to the pressurizable portion thereof.
Further in accordance with the present invention, there is provided a method of fabricating a pump diaphragm comprising the initial steps of forming the first and second layers from the above-described materials and with the above-described structural attributes. Subsequent to the formation of the first and second layers, the second layer is disposed into laminar juxtaposition with the first layer such that the outer peripheral portion of the second layer is nested within the outer peripheral portion of the first layer, and the inner peripheral portion of the second layer is nested within the inner peripheral portion of the first layer.